Lipid Biochemistry USMLE Step 1 Practice Question
A 45-year-old man with a 20-year history of type 2 diabetes presents with tendon xanthomas and eruptive skin xanthomas. Vital signs: BP 148/92 mmHg, HR 88 bpm, RR 16, temp 37°C. Laboratory findings reveal serum triglycerides 850 mg/dL, LDL cholesterol 320 mg/dL despite atorvastatin 80 mg daily, elevated apolipoprotein B levels, and normal TSH. He denies alcohol use. Which pathophysiologic mechanism best explains his severe dyslipidemia?
Answer choices
- AImpaired lipolysis due to lipoprotein lipase deficiency
- BDefective LDL receptor with complete loss of function
- CHepatic lipase deficiency leading to HDL accumulation
- DIncreased VLDL production and impaired remnant clearanceCorrect answer
- EFamilial LCAT deficiency with impaired cholesteryl ester formation
- FHypothyroidism causing secondary combined hyperlipidemia
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